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CS-RS-RP-009-12

Phase II Final Status Survey Report Mallinckrodt Columbium-Tantalum Plant

St. Louis, Missouri

Chapter 12

Project No. 137131 Revision 0

Prepared by: EnergySolutions, LLC Commercial Projects

1009 Commerce Park Drive, Suite 100 Oak Ridge, TN 37830

Authored By:

11-01-2013 Timothy J. Bauer, Health Physicist Date

Reviewed By: 11-01-2013 Joseph D. Jacobsen, Senior Health Physicist Date

Reviewed By: 11-01-2013 Mark Cambra, P.E., Project Manager Date

Approved By:

11-1-2013

Arthur J. Palmer, CHP, PMP, Director, Health Physics & Radiological Engineering Date

X Non-Proprietary X New Proprietary Title Change Restricted Information Revision Safeguards Information Rewrite Sensitive Security Information Cancellation Effective Date

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Typewritten Text

11-01-2013

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Phase II Final Status Survey Report Mallinckrodt CS-RS-RP-009-12 Columbium-Tantalum Plant, Chapter 12 Revision 0

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TABLE OF CONTENTS

Section 12.0 RESULTS SUMMARY FOR PLANT 5 SUBSURFACE SU06 ........................................5

Page

12.1 Overview ..................................................................................................................5 12.2 Remedial Action and Radiological Sampling Summary .........................................9 12.3 Data Collection ......................................................................................................10

12.3.1 Gamma Scans.............................................................................................10 12.3.2 Soil Sampling .............................................................................................10 12.3.3 Core Boring ................................................................................................17

12.4 Data Analysis .........................................................................................................17

12.4.1 Elevated Area Evaluation ..........................................................................17 12.4.2 Data Set Screening Analysis ......................................................................18 12.4.3 WRS Test ...................................................................................................20 12.4.4 Retrospective Analysis...............................................................................20

12.5 Dose Assessment of VCP ......................................................................................20

12.5.1 Verification of RESRAD v6.5 ...................................................................21 12.5.2 Elevated Area Characterization .................................................................21 12.5.3 In Situ Model and Results ..........................................................................22 12.5.4 Excavation Scenario Model and Results....................................................23 12.5.5 Dose Using Survey Unit Average ..............................................................24 12.5.6 Conclusion .................................................................................................25

12.6 Deviations ..............................................................................................................25 12.7 NRC Inspections ....................................................................................................25 12.8 Conclusion .............................................................................................................25 12.9 References ..............................................................................................................26

APPENDIX A Excerpts from RESRAD v6.5 Verification Runs ............................................27

APPENDIX B RESRAD v6.5 Summary Report for In Situ Model .........................................76

APPENDIX C RESRAD v6.5 Summary Report for Excavation Scenario Model ................105


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LIST OF FIGURES

Figure Page Figure 12-1 Location of SU06 in C-T Plant 5 ............................................................................... 6Figure 12-2 Photograph of SU06 Looking Southeast from East Side of Building 250 ................. 7Figure 12-3 Photograph of VCP Contents ..................................................................................... 7Figure 12-4 Photograph Looking West at the Terminus of the VCP Prior to Grouting ................ 7Figure 12-5 Post-Remediation Soil Sampling Locations ............................................................... 8Figure 12-6 GWS and Soil Sampling Locations .......................................................................... 12Figure 12-7 Additional Biased Soil Sampling Locations ............................................................ 13

LIST OF TABLES

Table Page Table 12-1 Post-Remediation Sampling Analytical Results .......................................................... 9Table 12-2 Gamma Spectroscopy Systematic Sample Analytical Results .................................. 15Table 12-3 Gamma Spectroscopy Biased Sample Analytical Results ......................................... 16Table 12-4 Characterization Borehole Results ............................................................................ 17Table 12-5 Screening Tests Results ............................................................................................. 19Table 12-6 Retrospective Analysis .............................................................................................. 20Table 12-7 Comparison of RESRAD Results .............................................................................. 21Table 12-8 RESRAD In Situ Model Parameter Values ............................................................... 22Table 12-9 RESRAD Excavation Scenario Model Parameter Values ......................................... 24


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% percent

ABBREVIATIONS AND ACRONYMS

σ sigma; standard deviation Ac actinium AECOM AECOM Technical Services bgs below grade surface C-T columbium-tantalum CFR Code of Federal Regulations DCGL derived concentration guideline level DP decommissioning plan DQO data quality objectives EMC elevated measurement comparison EnergySolutions, LLC EnergySolutions F exposure-weighted fraction of the DCGLW FSS Final Status Survey FSSR Final Status Survey Report ft feet ft2 square feet GWS gamma walk-over survey m meters m2 square meters MARSSIM Multi-Agency Radiation and Site Investigation Manual (NUREG-1575) MDC minimum detectable concentration mrem/yr millirem per year NIST National Institute of Standards and Technology NRC U.S. Nuclear Regulatory Commission Pa protactinium Pb lead pCi/g picoCuries per gram Ra radium SOF sum of fractions Th thorium U uranium VCP vitrified clay pipe WRS Wilcoxon Rank Sum


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12.0 RESULTS SUMMARY FOR PLANT 5 SUBSURFACE SU06

This chapter of the Final Status Survey Report (FSSR) presents the results of the final status survey (FSS) and data assessment for Plant 5 subsurface survey unit SU06 in accordance with Columbium-Tantalum (C-T) Phase II Decommissioning Plan (DP) Section 14.5. The FSS for this Class 1 survey unit was completed by AECOM Technical Services (AECOM) in September 2011. The SU06 data assessment was performed based on the assumptions, methods, and performance criteria established to satisfy the data quality objectives (DQOs) in accordance with the C-T Phase II DP Section 14.4.3.8. The summary statistics provide numerical values for measures of central tendency (i.e., mean, median), variation (i.e., standard deviation), and spread (i.e., minimum, maximum). Data evaluation and statistical analyses were performed and a separate decision was made for each survey unit of the C-T Plant as to its suitability for release for unrestricted use based upon the industrial use scenario release criterion as established in C-T Phase II DP Chapter 5.

12.1 OVERVIEW

SU06 is a Class 1 survey unit in the western portion of C-T Plant 5. The survey unit is approximately 393 square meters (m2) in size, which is less than the size limit of 3,000 m2 for Class 1 survey units for subsurface material (per C-T Phase II DP, Table 14-4). Class 1 was the appropriate classification because the survey unit contained residual radioactivity that exceeded the derived concentration guideline value (DCGLW) prior to remediation. Figure 12-1 shows the location of SU06 within the Plant 5 area.

Figure 12-2 is a photograph of SU06 as viewed from northwest of the survey unit looking south east. Portions of legacy concrete remain in the survey unit. The soil adjacent to Building 250 was removed down to the Building 250 grade beam and then along a 1-to-1 slope down to the final excavation depth. Additional excavation threatened to undermine the building foundation and existing water line running along the building and was not performed. Excavated depth ranged from 4 to 16 feet (ft). The sloped area adjacent to Building 250 was addressed as part of the FSS.

A vitrified clay pipe (VCP) containing contaminated material not associated with the C-T manufacturing operations was discovered running east-west through AECOM grids A4, B4, and C4. Figure 12-3 is a photograph of the VCP contents. The VCP was removed until within approximately 12 ft from the footprint of Building 250 in order to avoid undermining the manhole for the remaining sewer system. A sample of the pipe residue was collected (sample 3112), which reported radioactivity at a gross sum of fractions (SOF) value of more than 100. A sample of the soil collected from the trench after VCP removal indicated that the radioactivity was confined to the VCP (sample 3111 with a gross SOF of 0.19). The terminus of the VCP was cleaned as far back as practical (approximately 5 ft), grouted, and abandoned in place. The portion of the VCP remaining in place (approximately 7 ft) within SU06 was assumed to contain pipe residue consistent with sample 3112. Figure 12-4 is a photograph of the VCP terminus prior to grouting. The location of the VCP and referenced AECOM grids are shown on Figure 12-5.


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Figure 12-1 Location of SU06 in C-T Plant 5


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Figure 12-2 Photograph of SU06 Looking Southeast from East Side of Building 250

Figure 12-3 Photograph of VCP Contents

Figure 12-4 Photograph Looking West at the Terminus of the VCP Prior to Grouting


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Figure 12-5 Post-Remediation Soil Sampling Locations


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12.2 REMEDIAL ACTION AND RADIOLOGICAL SAMPLING SUMMARY

Post-remediation soil sampling, shown in Figure 12-5 above, was performed by AECOM and included: 1) “Grid + Step-Out Sampling”, 2) “Sloped Area Characterization” sampling, 3) “At-Depth (Auger) Sampling”, and 4) miscellaneous characterization before and after VCP removal. All post-remediation soil samples were analyzed at the on-site laboratory only. Table 12-1 provides the results for the 15 “Grid + Step-Out” samples, 5 “Sloped Area Characterization” samples, 9 “At-Depth (Auger)” samples, and 9 VCP characterization samples.

The trench excavated during VCP removal was subjected to gamma walk-over survey (GWS) and soil sampling, including a soil sample collected immediately beneath the terminus (sample 3111). Soil sample results from both the trench and spoils indicate the high levels of contamination found in the VCP were wholly or largely contained in the VCP for the length of pipe excavated and removed.

Table 12-1 Post-Remediation Sampling Analytical Results

Sample ID

Collection Date

On-Site Results Concentration (pCi/g) Gross

SOF a 232Th 226Ra 238U “Grid + Step-Out”

3018 7/18/2011 1.51 13.6 9.47 0.54 3048

8/4/2011 1.11 3.82 9.39 0.19

3051 0.95 4.47 7.81 0.20 3052 1.40 3.20 8.03 0.18 3065 8/10/2011 4.90 11.98 18.56 0.64 3066 1.47 6.26 23.6 0.31 3070 8/11/2011 1.14 3.61 37.7 0.23 3077 8/12/2011 0.28 3.92 19.8 0.18 3078 -0.74 7.85 17.2 0.30 3099 8/16/2011 4.00 5.27 25.9 0.39 3127 8/27/2011 1.14 1.95 1.87 0.12 3132

8/29/2011 1.04 1.34 2.78 0.09

3133 1.30 2.16 4.15 0.13 3134 1.15 1.05 1.95 0.09 3160 9/7/2011 4.18 14.1 20.8 0.69

“Sloped Area Characterization” 0791 5/3/2011 24.3 30.9 18.9 2.08 0853 5/20/2011 4.05 5.01 21.0 0.37 3028

8/1/2011 2.36 5.66 15.5 0.32

3029 0.00 4.27 3.02 0.15 3030 1.33 4.02 3.82 0.20


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Table 12-1 Post-Remediation Sampling Analytical Results (continued)

Sample ID

Collection Date

On-Site Results Concentration (pCi/g) Gross

SOF a 232Th 226Ra 238U “At-Depth (Auger)”

3001

6/24/2011

3.42 10.8 31.9 0.56 3002 1.10 1.59 1.13 0.10 3003 1.47 1.56 1.50 0.12 3004 1.39 1.92 1.36 0.13 3005 1.39 1.19 0.72 0.10 3085

8/16/2011 1.12 5.63 44.9 0.31

3086 0.79 3.37 9.79 0.16 3090 1.08 2.53 9.68 0.15 3139 8/30/2011 1.31 2.46 16.0 0.16

Miscellaneous Characterization (sludge in VCP) 3112 8/25/2011 708.2 2,127.7 415.4 102.07

Miscellaneous Characterization (after VCP removal) 3062 8/10/2011 1.30 2.72 6.16 0.16 3111 8/28/2011 1.23 3.73 4.47 0.19 3113 8/25/2011 6.45 4.97 16.5 0.47 3114

8/26/2011

4.71 9.63 21.35 0.56 3115 3.74 12.45 28.83 0.63 3117 1.25 2.15 7.12 0.14 3119 0.32 0.22 12.28 0.04 3128 8/27/2011 1.45 2.88 12.86 0.18

a Bolded orange SOF values indicate a result >0.5 but ≤1 and bolded red SOF values indicate a result >1.

12.3 DATA COLLECTION

Data collection was performed based on the assumptions, methods, and performance criteria established to satisfy the DQOs in accordance with the C-T Phase II DP, Sections 14.4.1 and 14.4.3. Details regarding FSS design and quality assurance and quality control applicable to all survey units were discussed in Chapters 4 and 5, respectively, of this FSSR.

12.3.1 Gamma Scans

A GWS was performed over 100% of the excavated area to locate radiation anomalies that might indicate areas with elevated residual radioactivity where further data collection (i.e., biased soil sampling) was warranted.

12.3.2 Soil Sampling

Soil samples to be used for the statistical test were collected at a frequency and at representative locations throughout SU06 such that a statistically sound conclusion regarding the radiological condition of the survey unit could be developed. Biased soil samples were collected at locations of elevated residual radioactivity near the manhole identified by GWS as well as along the sloped excavation along Building 250. Figure 12-6 provides the GWS results and soil sampling locations. Post-remedial sampling around the manhole identified elevated residual radioactivity


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(sample 0791) in an area of less than 10 m2. The manhole area (as shown in Figure 12-5) was excavated down to the building footer and additional excavation to remove the residual radioactivity threatened to undermine the building foundation. Figure 12-7 shows the sloped excavation samples for bounding elevated contamination identified near the manhole. A total of 26 soil samples were collected throughout SU06, 17 over the areal footprint of SU06 (15 systematic and 2 GWS biased) and 9 biased for elevated area bounding of the manhole in the sloped excavation along Building 250. Further excavation threatened to undermine the building foundation and therefore additional sampling was performed in order to evaluate the residual contamination.


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Figure 12-6 GWS and Soil Sampling Locations


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Figure 12-7 Additional Biased Soil Sampling Locations


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All soil samples were analyzed on site via gamma spectroscopy analysis. Table 12-2 provides the sample results and summary statistics for the 15 systematic samples. Table 12-3 provides the sample results for the 2 GWS biased samples and the 9 biased samples for elevated area bounding of the sloped excavation along Building 250—some of the results in Table 12-3 are duplicated from Table 12-1.

Any remaining sieved material from each sample was analyzed separately to verify residual radioactivity was consistent with sample results. The radiological screening process did not identify any significant levels of radioactivity in the sieved materials removed from samples.

The C-T Phase II DP, Table 4-17, provided mean background activity levels of 1.3, 2.5, and 4.4 picoCuries per gram (pCi/g) for thorium-232 (232Th), radium-226 (226Ra), and uranium-238 (238U), respectively. These values were used to calculate net SOF values—note that when measured activity concentration levels were less than the background mean resulting in a negative value, the net activity concentration was set equal to zero for the net SOF calculation.

To mitigate the risk of backfilling, the on-site laboratory analytical results were reviewed to determine the likelihood of the survey unit failing to meet the criteria for radiological release. The on-site laboratory, by design, reported conservative sample results.


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Table 12-2 Gamma Spectroscopy Systematic Sample Analytical Results

Sample ID

Depth (ft bgs)

On-Site Results Off-Site Results a On-Site/ Off-Site Gross SOF Ratio

Activity Concentration (pCi/g) b SOF c Activity Concentration (pCi/g) b

SOF c 232Th 226Ra 238U 232Th 226Ra 238U

Result Uncert. (2σ) MDC Result Uncert.

(2σ) MDC Result Uncert. (2σ) MDC Gross Net d Result Uncert.

(2σ) MDC Result Uncert. (2σ) MDC Result Uncert.

(2σ) MDC Gross Net d

3163 9 2.32 0.37 0.09 4.32 1.80 1.37 12.00 3.05 2.02 0.26 0.12 2.37 0.43 0.39 2.98 0.40 0.10 3.38 0.43 0.11 0.21 0.06 1.27 3164 10 1.07 0.23 0.06 2.28 1.47 1.15 10.01 1.71 0.89 0.14 0.01 1.58 0.50 0.32 1.86 0.28 0.09 2.05 0.29 0.10 0.13 0.01 1.03 3165 13 5.36 0.58 0.14 13.88 2.07 1.33 5.34 1.68 1.18 0.70 0.56 7.32 1.10 0.54 14.10 1.80 0.14 15.90 2.00 0.16 0.81 0.66 0.87 3166 13 4.05 0.48 0.11 1.84 1.39 1.09 7.17 1.74 1.07 0.24 0.12 5.66 0.84 0.40 2.16 0.32 0.10 2.95 0.41 0.11 0.31 0.18 0.77 3167 12 1.75 0.34 0.06 2.14 1.62 1.27 10.44 1.80 0.94 0.16 0.03 2.31 0.31 0.09 2.10 0.29 0.08 2.31 0.31 0.09 0.17 0.04 0.94 3168 12 2.11 0.39 0.09 1.61 1.75 1.39 10.09 1.53 0.90 0.16 0.04 2.14 0.59 0.36 1.88 0.28 0.10 2.16 0.31 0.10 0.16 0.04 1.00 3169 10 3.32 0.45 0.10 7.47 2.40 1.82 26.40 2.61 1.26 0.43 0.28 4.49 0.89 0.60 4.78 0.65 0.16 5.19 0.74 0.17 0.36 0.21 1.20 3170 13 1.28 0.26 0.05 2.19 0.83 0.56 0.79 1.21 0.97 0.13 0.00 1.12 0.25 0.21 1.17 0.17 0.06 1.31 0.18 0.05 0.09 0.00 1.46 3171 13 1.10 0.21 0.06 2.06 0.85 0.60 1.65 0.80 0.53 0.12 0.00 1.14 0.40 0.37 1.71 0.27 0.11 1.60 0.24 0.11 0.11 0.00 1.10 3172 13.5 2.11 0.30 0.10 0.90 1.34 1.08 0.00 1,535.80 1.99 0.12 0.03 3.30 0.54 0.26 1.30 0.20 0.07 1.83 0.25 0.08 0.18 0.08 0.64 3173 10 1.25 0.34 0.14 5.51 1.74 1.28 11.97 1.72 0.91 0.26 0.11 1.60 0.43 0.45 4.99 0.65 0.11 5.83 0.73 0.13 0.24 0.10 1.05 3174 13.5 1.92 0.37 0.14 3.59 1.98 1.53 14.24 2.12 1.07 0.22 0.08 2.43 0.54 0.41 3.07 0.42 0.11 3.47 0.47 0.12 0.21 0.07 1.05 3175 14 1.55 0.25 0.09 2.14 1.03 0.76 4.71 1.00 0.63 0.14 0.01 1.91 0.33 0.22 2.09 0.28 0.07 2.34 0.31 0.07 0.15 0.03 0.93 3176 13 1.11 0.23 0.09 1.55 0.87 0.64 3.30 3.01 2.14 0.10 0.00 1.03 0.36 0.32 1.30 0.21 0.09 1.35 0.21 0.09 0.09 0.00 1.17 3177 11 1.03 0.27 0.08 5.64 1.66 1.18 9.30 1.29 0.69 0.25 0.11 1.15 0.28 0.26 3.97 0.51 0.07 4.47 0.56 0.08 0.19 0.05 1.31

Summary Statistics Count: 15

15

15

15 15 15

15

15

15 15 15 Average: 2.09 3.81 8.49 0.23 0.10 2.64 3.30 3.74 0.23 0.10 1.05 Median: 1.75 2.19 9.30 0.16 0.04 2.14 2.10 2.34 0.18 0.05 1.05 Standard Dev.: 1.25 3.35 6.65 0.16 0.15 1.84 3.23 3.63 0.18 0.17 0.21 Minimum: 1.03 0.90 0.00 0.10 0.00 1.03 1.17 1.31 0.09 0.00 0.64 Maximum: 5.36 13.88 26.40 0.70 0.56 7.32 14.10 15.90 0.81 0.66 1.46 Range: 4.33 12.97 26.40 0.60 0.56 6.29 12.93 14.59 0.72 0.66 0.81

a Off-site laboratory results as reported by TestAmerica after sufficient in-growth time to reach 226Ra progeny equilibrium. b Italicized results indicate <MDC. c Bolded orange SOF values indicate a result >0.5 but ≤1 and bolded red SOF values indicate a result >1. d Calculated as discussed in Section 12.3.2.


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Table 12-3 Gamma Spectroscopy Biased Sample Analytical Results

Sample ID

Depth (ft bgs)

On-Site Results Off-Site Results a On-Site/ Off-Site Gross SOF Ratio

Activity Concentration (pCi/g) b SOF c Activity Concentration (pCi/g) b

SOF c 232Th 226Ra 238U 232Th 226Ra 238U

Result Uncert. (2σ) MDC Result Uncert.

(2σ) MDC Result Uncert. (2σ) MDC Gross Net d Result Uncert.

(2σ) MDC Result Uncert. (2σ) MDC Result Uncert.

(2σ) MDC Gross Net d

GWS Biased Samples 3196 13.5 1.56 0.30 0.09 7.62 2.74 2.13 41.52 3.23 1.36 0.38 0.24 1.97 0.57 0.48 4.29 0.60 0.12 4.56 0.59 0.14 0.23 0.09 1.63 3197 13 7.42 0.67 0.17 2.96 1.61 1.24 6.28 2.02 1.33 0.42 0.27 11.10 1.50 0.56 2.49 0.38 0.15 2.91 0.42 0.16 0.55 0.41 0.76

Manhole Biased Samples 0791 -- 24.35 1.27 0.25 30.39 2.37 1.37 18.86 1.88 1.24 2.08 1.93

Samples Not Sent to Off-Site Laboratory

0804 -- 0.80 0.10 0.05 1.53 0.46 0.33 1.53 0.44 0.29 0.09 0.00 0805 -- 1.73 0.22 0.05 3.82 1.04 0.78 10.36 1.09 0.56 0.22 0.07 0853 -- 4.05 0.32 0.09 5.01 1.46 1.12 21.00 1.77 0.84 0.37 0.22 3028 5 2.36 0.37 0.12 5.66 2.28 1.76 15.46 1.79 1.01 0.31 0.17 3029 2.5 0.00 379.98 0.25 4.27 1.11 0.76 3.02 0.91 0.57 0.15 0.06 3030 6.5 1.33 0.24 0.06 4.02 1.06 0.74 3.82 1.03 0.63 0.20 0.05 3066 10 1.47 0.31 0.07 6.26 2.42 1.85 23.57 2.31 1.05 0.31 0.16 3163 9 2.32 0.37 0.09 4.32 1.80 1.37 12.00 3.05 2.02 0.26 0.12

a Off-site laboratory results as reported by TestAmerica after sufficient in-growth time to reach 226Ra progeny equilibrium. b Italicized results indicate <MDC. c Bolded orange SOF values indicate a result >0.5 but ≤1. d Calculated as discussed in Section 12.3.2.


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12.3.3 Core Boring

C-T Phase II DP Table 4-7 provided characterization borehole results. Of the locations provided in the table, two were collected within the extent of SU06: BH-009 and BH-030. Table 12-4 provides the data for these locations. The results indicate that beyond the excavation extent, additional subsurface contamination is not reasonably expected. Therefore, in accordance with Page 14-22 of the C-T Phase II DP, FSS core sampling or measurements were not performed.

Table 12-4 Characterization Borehole Results

Location ID Sample Depth (ft)

Activity Concentration (pCi/g) a SOF b

232Th 226Ra 238U Gross Net c

BH-009 2 - 3 5.50 16.30 3.80 0.79 0.65

BH-030

2 - 3 1.60 3.50 28.20 0.23 0.08 3 - 4 0.77 2.52 4.03 0.12 0.00 4 - 5 0.84 2.20 5.79 0.12 0.00

10 - 11 0.69 1.29 9.76 0.09 0.01 12 - 13 2.60 1.30 14.60 0.17 0.07 14 - 15 1.40 0.84 6.30 0.10 0.01

a Italicized results indicate < MDC. b Bolded orange SOF values indicate a result >0.5 but ≤1. c Calculated as discussed in Section 12.3.2.

12.4 DATA ANALYSIS

Data analysis was performed based on the assumptions, methods, and performance criteria established to satisfy the DQOs in accordance with the C-T Phase II DP, Sections 14.4.1 and 14.4.3. Details regarding FSS design and quality assurance and quality control applicable to all survey units were discussed in Chapters 4 and 5, respectively, of this FSSR.

12.4.1 Elevated Area Evaluation

AECOM provided a preliminary evaluation of the elevated area. For an estimated area of less than 10 m2, the area factor from C-T Phase II DP Figure 5-3 was 2.4. Based on sample 0791, the elevated area’s measured concentration SOF value was 2.1.

Equation 9 from C-T Phase II DP, Section 5.8.7 provides for the calculation of an Index value that represents the fraction or multiple of the DCGLEMC. If the Index value is greater than one, then the DCGLEMC is exceeded. Using the elevated area extents determined by AECOM, parameters necessary to calculate the Index value for Elevated Area #1 were:

• The elevated area activity levels based on sample 0791 were 24.35, 30.39, and 18.86 pCi/g for 232Th, 226Ra, and 238U, respectively (from Table 12-3 above);

• Mean background activity levels were 1.3, 2.5, and 4.4 pCi/g for 232Th, 226Ra, and 238U, respectively (from C-T Phase II DP Table 4-17);


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• The size of the elevated area was less than 10 m2; and,

• The area factors from C-T Phase II DP Figure 5-3 for the elevated area were 2.2, 2.4, and 3.3 for 232Th, 226Ra, and 238U, respectively.

The calculation of the Index value is shown below. Because the Index value as calculated in accordance with the DP was less than one, this elevated area is compliant with the C-T Phase II DP for elevated measurements in soil.

𝐼𝑛𝑑𝑒𝑥 =(24.35 − 1.3) 𝑝𝐶𝑖/𝑔

(2.2 × 23.9 𝑝𝐶𝑖/𝑔)𝑇ℎ 𝑠𝑒𝑟𝑖𝑒𝑠+

(30.39− 2.5) 𝑝𝐶𝑖/𝑔(2.4 × 29.4 𝑝𝐶𝑖/𝑔)𝑅𝑎226

+(14.46− 4.4) 𝑝𝐶𝑖/𝑔(3.3 × 721 𝑝𝐶𝑖/𝑔)𝑈

= 0.84

The portion of the VPC remaining in SU06 is assumed to have the same contents as the removed portions and that the radioactivity levels are consistent with sample 3112. The length of VCP remaining in SU06 is approximately 7 ft and the VCP diameter is assumed to be no larger than 12 inches (1 ft). Parameters necessary to calculate the Index value for the VPC, or Elevated Area #2, were:

• The elevated area activity levels based on sample 3112 were 708.2, 2,127.7, and 415.4 pCi/g for 232Th, 226Ra, and 238U, respectively (from Table 12-1 above);

• Mean background activity levels were 1.3, 2.5, and 4.4 pCi/g for 232Th, 226Ra, and 238U, respectively (from C-T Phase II DP Table 4-17);

• The size of the elevated area was approximately 7 square feet (ft2) or 0.7 m2; and,

• The area factors from C-T Phase II DP Figure 5-3 for the elevated area were 2.2, 2.4, and 3.3 for 232Th, 226Ra, and 238U, respectively.

The calculation of the Index value is shown below. Because the Index value as calculated in accordance with the DP was greater than one, this elevated area is not compliant with the C-T Phase II DP for elevated measurements in soil. Section 12.5 discusses a dose assessment performed to evaluate the impact of this area that is not compliant with the DCGLs.

𝐼𝑛𝑑𝑒𝑥 =(708.2 − 1.3) 𝑝𝐶𝑖/𝑔

(2.2 × 23.9 𝑝𝐶𝑖/𝑔)𝑇ℎ 𝑠𝑒𝑟𝑖𝑒𝑠+

(2,127.7− 2.5) 𝑝𝐶𝑖/𝑔(2.4 × 29.4 𝑝𝐶𝑖/𝑔)𝑅𝑎226

+(415.4− 4.4) 𝑝𝐶𝑖/𝑔(3.3 × 721 𝑝𝐶𝑖/𝑔)𝑈

= 43.7

12.4.2 Data Set Screening Analysis

Table 12-5 summarizes the results of the screening tests performed in accordance with Pages 14-27 through 14-29 of the C-T Phase II DP. All applicable tests demonstrating compliance passed.


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Table 12-5 Screening Tests Results

Screening Test Test Value Conclusion Min/Max 0.79 PASS

Low Level N/A Not applicable; Class 1 survey unit DCGL N/A Not applicable; Min/Max < 1

EMC Limit 0.25 PASS

12.4.2.1 Min/Max

In accordance with Page 14-27 of the C-T Phase II DP, the Min/Max screening test value was calculated by subtracting the minimum reference area result from the maximum survey unit systematic result. Sample 3165 with a gross SOF of 0.81 (from Table 12-2) was the maximum survey unit systematic result. Sample BH-Z-08 with a calculated gross SOF of 0.02 (from C-T Phase II DP Table B-1) was the minimum reference area result. The Min/Max screening test value was calculated to be 0.79. Because the test value was less than one, further computations are not required, i.e., DCGLW screening and Wilcoxon Rank Sum (WRS) tests.

12.4.2.2 Low Level

In accordance with Page 14-27 of the C-T Phase II DP, the Low Level screening test is not applicable to Class 1 survey units.

12.4.2.3 DCGLW

In accordance with Page 14-28 of the C-T Phase II DP and because the Min/Max test value was less than one, the DCGLW screening test was not applicable to this survey unit.

12.4.2.4 EMC Limit

In accordance with Page 14-28 of the C-T Phase II DP, the elevated measurement comparison (EMC) limit screening test was applied to the two elevated areas: #1 around the manhole (sample 0791) and #2 the VCP (sample 3112). Parameters necessary to calculate the exposure-weighted fraction of the DCGLW, F, were:

• The size of the elevated areas were determined to be less than 10 m2 for area #1 and approximately 0.7 m2 for area #2;

• The area factor from C-T Phase II DP Figure 5-3 for both elevated areas was conservatively set to 2.2 (based on thorium series only);

• The elevated area activity level was conservatively represented by sample 0791 with a gross SOF = 2.08 and by sample 3112 with a gross SOF of 102.07 for areas #1 and #2, respectively; and,

• The survey unit average was a gross SOF = 0.23 (from Table 12-2).


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The calculation of the EMC screening test result is shown below, using C-T Phase II DP Equation 14-7. A separate term was included for each elevated area.

𝐹 = �10 𝑚2

393 𝑚2 ×2.08

2.2 × 1� + �

0.7 𝑚2

393 𝑚2 ×102.072.2 × 1

� + �(393 − 10 − 0.7) 𝑚2

393 𝑚2 ×0.23

1� = 0.33

In accordance with the C-T Phase II DP and because the result was less than one, the total radioactivity concentration in the survey unit is within the release criterion. However, elevated area #2 (VCP) failed the elevated area evaluation and is evaluated using a dose assessment in Section 12.5.

12.4.3 WRS Test

In accordance with Page 14-29 of the C-T Phase II DP and because the Min/Max test value was less than one, the WRS Test was not required to demonstrate compliance.

12.4.4 Retrospective Analysis

A retrospective analysis was performed of the FSS results to determine whether the results met the survey design objectives, in accordance with Page 14-30 of the C-T Phase II DP. Table 12-6 provides the results of the retrospective analysis. Because the actual sample size exceeded the retrospective value sample size, the conclusion is that the survey design objectives were met.

Table 12-6 Retrospective Analysis

Parameter A Priori Value Retrospective Value Based on FSS Results (Gross SOF)

Upper Bound of Gray Region DCGL = 1 1 Lower Bound of Gray Region 0.5 x DCGL = 0.5 0.23

Spatial Variability (standard deviation) 1/6 x DCGL = 0.17 0.18 Type I Error (false positive) 0.05 0.05

Type II Error (false negative) 0.05 0.05 Relative Shift 3 4.2

Calculated N/2 Sample Size 15 a 9 Actual N/2 Sample Size -- 15

a The a priori value of 15 for the N/2 sample size was determined to be a conservative value that would allow application of either the Sign or WRS test. The a priori value for N/2 is 10 based on MARSSIM Table 5.3.

12.5 DOSE ASSESSMENT OF VCP

The elevated area evaluation (Section 12.4.1) calculated an Index value of 43.7 for Elevated Area #2 (VCP). Because this value was greater than one, the elevated area failed to demonstrate compliance using the DCGLs developed in C-T Phase II DP Chapter 5. As an alternative, this section presents the results of a dose assessment to evaluate the elevated area.


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12.5.1 Verification of RESRAD v6.5

C-T Phase II DP Chapter 5 presented three dose models (cases) in the development of the DCGLs. 408guti, 407guti, and 399guti were the RESRAD v6.4 cases for the thorium series, natural uranium, and “6 230Th + 226Ra + 210Pb,” respectively. EnergySolutions was currently using RESRAD v6.5; therefore, to ensure comparable results, the three cases mentioned were run in the later version. Excerpts of the RESRAD v6.5 runs are provided in Appendix A. Table 12-7 compares selected results from RESRAD v6.4 and v6.5 for the three cases.

Table 12-7 Comparison of RESRAD Results

RESRAD Calculation RESRAD Result a v6.4 v6.5

408guti (thorium series) Maximum TDOSE(t) (mrem/yr) 7.627 7.627 Probabilistic total dose, year 0, Avg (mrem/yr): 228Ra 228Th 232Th All

2.87E+00 3.33E+00 3.48E-01 6.54E+00

2.87E+00 3.33E+00 3.48E-01 6.54E+00

407guti (natural uranium) Maximum TDOSE(t) (mrem/yr) 2.429E-01 2.429E-01 Probabilistic total dose, year 0, Avg (mrem/yr): 238U 234U 235U 231Pa 227Ac All

7.66E-02 1.79E-02 1.47E-02 2.97E-02 7.77E-02 2.17E-01

7.63E-02 1.79E-02 1.47E-02 2.97E-02 7.74E-02 2.16E-01

399guti (6 230Th + 226Ra + 210Pb) Maximum TDOSE(t) (mrem/yr) 1.242E+01 1.242E+01 Probabilistic total dose, year 150, Avg (mrem/yr): 230Th 226Ra 210Pb All

1.65E+00 3.67E+00 2.66E-03 5.33E+00

1.65E+00 3.67E+00 2.66E-03 5.33E+00

a Bolded results indicate difference between two RESRAD versions.

In conclusion, RESRAD v6.5 provided identical or comparable results to RESRAD v6.4 and therefore RESRAD v6.5 was used to perform the dose assessment of the VCP.

12.5.2 Elevated Area Characterization

12.5.2.1 Elevated Area Size

Elevated Area #2 had a footprint of 7 ft2 or 0.7 m2. The elevated radioactivity was limited to the contents of the VCP, which was assumed to be no greater than 12 in; therefore, the contamination thickness was 0.3 m.


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12.5.2.2 Radionuclide Concentrations

Elevated Area #2 gross activity levels, represented by sample 3112 were 708.2, 2,127.7, and 415.4 pCi/g for 232Th, 226Ra, and 238U, respectively (from Table 12-1). The elevated area net activity levels were 706.9, 2,125.2, and 411.0 pCi/g for 232Th, 226Ra, and 238U, respectively.

12.5.3 In Situ Model and Results

12.5.3.1 RESRAD Model

The C-T Phase II DP Chapter 5 RESRAD models 408guti, 407guti, and 399guti were identical except for the entered radionuclide concentrations. Three models were run in order to develop independent DCGLs. For this elevated area, the actual radionuclide concentrations were established based on sampling and therefore independent models were not required. Table 12-8 provides the RESRAD in situ model parameters that were changed from the C-T Phase II DP Chapter 5 RESRAD models and the justification for each change.

Table 12-8 RESRAD In Situ Model Parameter Values

Parameter Value Justification Soil Concentrations

228Ra, 228Th, and 232Th 706.9 pCi/g Thorium series in secular equilibrium per C-T Phase II DP Section 5.8.2. Average net 232Th concentration from Section 12.5.2.2.

226Ra and 210Pb 2,125.2 pCi/g

226Ra and progeny in secular equilibrium per C-T Phase II DP Section 5.8.4. Average net 226Ra concentration from Section 12.5.2.2.

230Th 12,751.2 pCi/g

230Th was not measured in FSS samples. The 230Th / 226Ra ratio of 6 was assumed per C-T Phase II DP Section 5.8.4.

238U and 234U 411.0 pCi/g For natural uranium, the concentrations of 238U and 234U are equal per C-T Phase II DP Section 5.8.3. Average net 238U concentration from Section 12.5.2.2.

235U, 231Pa, and 227Ac 18.7 pCi/g 235U and progeny in naturally-occurring proportion (235U / 238U = 0.0455) per C-T Phase II DP Section 5.8.3.

Contaminated Zone Area 0.7 m2 Bounding area as discussed in Section 12.5.2.1. Thickness 0.3 m Thickness of the VCP as discussed in Section 12.5.2.2.

Cover/Hydrol. Cover depth 4.6 m AECOM did not note the depth of the VCP. It was

assumed to be installed at 16 ft bgs. Therefore, there would be 15 ft or 4.6 m of cover (non-contaminated off-site backfill).

12.5.3.2 Result

The maximum dose was 9.136E-14 millirem per year (mrem/yr) at year 1,000. Appendix B provides the RESRAD summary report.


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12.5.4 Excavation Scenario Model and Results

In addition to evaluating the dose from the elevated area in situ, an excavation scenario was developed to evaluate the dose if the contaminated material was exposed. It is unlikely, based on the future use scenario described in C-T Phase II DP Chapter 5, that large areas of contaminated material would be exposed during future site activities. No building foundations or basements are expected to be installed at the site. Utility systems are likely to be installed and most systems are installed in the 6 ft bgs depth range; however, the specific depth of the elevated area is not evaluated in this scenario.

The scenario assumes that the elevated area is completely exposed during activities to create a 3-ft (0.9-m) wide trench to the shallowest depth of the elevated area. The critical receptor will be exposed to the entire elevated area. The length of the trench would be equal to the length of the elevated area, which is 7 ft or 2.1 m. The critical receptor is an industrial worker, but not the same individual as that evaluated using the DCGLs, e.g. a contractor is performing the work.

It is assumed that the industrial worker will spend a total of 0.5 hours per meter of trench. Examples of activities being performed include trench bottom preparation, such as leveling aggregate, and pipe joining, such as welding. Total time in this trench would be 1 hour (0.5 hours per meter of trench × 2.1 m length). RESRAD evaluates dose on an annual basis. Therefore, 1 hour out of a year’s time would be an outdoor time fraction of 0.00011 hours (1 hour / 8,766 hours). Indoor time fraction is zero since this is not an indoor scenario.

12.5.4.1 RESRAD Model

Similar to the in situ model discussed in Section 12.5.3.1, one RESRAD model was developed for the excavation scenario. Table 12-9 provides the RESRAD excavation scenario model parameters that were changed from the C-T Phase II DP Chapter 5 RESRAD models and the justification for each change.


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Table 12-9 RESRAD Excavation Scenario Model Parameter Values

Parameter Value Justification Soil Concentrations

228Ra, 228Th, and 232Th 706.9 pCi/g Thorium series in secular equilibrium per C-T Phase II DP Section 5.8.2. Average net 232Th concentration from Section 12.5.2.2.

226Ra and 210Pb 2,125.2 pCi/g 226Ra and progeny in secular equilibrium per C-T Phase II DP Section 5.8.4. Average net 226Ra concentration from Section 12.5.2.2.

230Th 12,751.2 pCi/g 230Th was not measured in FSS samples. The 230Th / 226Ra ratio of 6 was assumed per C-T Phase II DP Section 5.8.4.

238U and 234U 411.0 pCi/g For natural uranium, the concentrations of 238U and 234U are equal per C-T Phase II DP Section 5.8.3. Average net 238U concentration from Section 12.5.2.2.

235U, 231Pa, and 227Ac 18.7 pCi/g 235U and progeny in naturally-occurring proportion (235U / 238U = 0.0455) per C-T Phase II DP Section 5.8.3.

Contaminated Zone Area 0.7 m2 Contaminated trench area equal to size of elevated area,

or 0.7 m2. Thickness 0.30 m C-T Phase II DP Appendix D, Page D-17, documents

that for the radionuclide mixture used to develop the DCGLs that the maximum dose rate by direct radiation is reached asymptotically when the contaminated zone thickness reaches about 30 cm. Additional contaminated zone thickness does not result in additional dose. This is also the thickness of the VCP as discussed in Section 12.5.2.2.

Occupancy, Inhalation, and External Gamma Data Indoor time fraction 0 No internal exposure applicable for the critical receptor

within a trench. Outdoor time fraction 0.00011 hours 1 hour for this length of trench within any given

modeled year.

12.5.4.2 Result

The maximum dose was 2.450E-01 mrem/yr at year 0. Appendix C provides the RESRAD summary report.

12.5.5 Dose Using Survey Unit Average

Table 12-2 provided the systematic sample results for the excavated surface. The average net SOF for the off-site summary statistics was 0.10. This corresponds to a dose of 2.5 mrem/yr.


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12.5.6 Conclusion

Adding together the in situ dose of 9.136E-14 mrem/yr and the maximum dose from the survey unit average of 2.5 mrem/yr, the as-left total dose from the survey unit is 2.5 mrem/yr for the critical receptor.

The independently-evaluated excavation scenario dose was 0.25 mrem/yr.

12.6 DEVIATIONS

In accordance with the second bullet in Section 14.5 of the C-T Phase II DP, the FSSR is required to list changes made in the FSS from what was proposed in the DP. Three deviations were noted.

1. Page 14-22 of the C-T Phase II DP indicated: “A plugged sewer would not be usable and not be salvageable as they are clay or concrete and would break into pieces upon excavation. In the future, potential exposure as a consequence of inadvertent intrusion would be similar to that posed by other subsoil at that depth in the remainder of the survey unit. Thus, if plugged sewers and their contents will be considered as part of the subsurface final status survey unit in which they are located.” AECOM sampled and cleaned out the VCP to a length of 5 ft from the opening and then grouted the pipe. However, AECOM did not perform any sampling of material remaining in the VCP after remediation and therefore the VCP remaining contents are assumed to be consistent with the sampled contents (sample 3112).

2. Page 14-27 of the C-T Phase II DP indicated that the “data set for the survey unit will be processed within a database using screening software developed and verified for the project.” This database was not developed; instead, a combination of Microsoft® Excel® spreadsheets and hand calculations was utilized. This deviation is not significant and does not affect the data collection or assessment.

12.7 NRC INSPECTIONS

A summary of NRC inspections applicable to the FSS are provided in Section 5.8 of this FSSR. The scope of the inspections included, but was not limited to: review of project plans, interviewing of project personnel, evaluation of the on-site laboratory, and independent confirmatory surveys conducted by the NRC after backfilling. Inspection Report 040-06563/11-003 noted that the NRC reviewed the FSS data package for SU06 to ensure the licensee conducted the surveys in accordance with the NRC-approved DP and work plans. No violations were identified. No findings of significance were identified.

12.8 CONCLUSION

FSS data were verified to be reliable, appropriately documented, and technically defensible. Specifically, the following conclusions are made:

• The instruments used to collect the data were capable of detecting the radiation type (i.e., gamma) at or below the release criteria (described in Sections 4.4 and 4.5 of this FSSR).


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• The calibration of the instruments used to collect the data was current and radioactive sources used for calibration were National Institute of Standards and Technology (NIST) traceable (described in Section 5.4 of this FSSR). Specific records available upon request.

• Instrument response was checked before instrument use each day, at minimum (described in Section 5.4 of this FSSR). Specific records available upon request.

• The survey methods used to collect the data were appropriate for the media and type of radiation being measured (described in Sections 4.4, 4.5, and 4.6 of this FSSR).

• The custody of samples collected for laboratory analysis was tracked from the point of collection until final results were obtained (described in Section 5.5.2 of this FSSR). Specific records available upon request.

• The survey data consist of qualified measurement results that are representative of the area of interest.

• Areas identified with elevated residual radioactivity (i.e. SOF > 1.0) were appropriately investigated and the DCGLEMC properly applied.

All the applicable screening tests passed, the retrospective analysis found that the survey design objectives were met, and additional subsurface contamination was not reasonably suspected. SU06 meets the industrial use scenario release criterion as established in the C-T Phase II DP Chapter 5; and therefore, satisfies the unrestricted release provisions of Title 10, Code of Federal Regulations (CFR), Part 20, Subpart E.

12.9 REFERENCES

Mallinckrodt, Mallinckrodt Columbium-Tantalum Phase II Decommissioning Plan, Revision 2, August 2008.


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APPENDIX A

Excerpts from RESRAD v6.5 Verification Runs

(408guti, 407guti, and 399guti)

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